Online - 2455-3891 Vol 13, Issue 4, 2020 Print - 0974-2441 Research Article POST-GLENOID FORAMEN: A RARE EMISSARY FORAMEN IN HUMAN SKULL

PRIYA G1*, YASODAI R2 1Department of Anatomy, RVS Dental College and Hospital, Coimbatore, Tamil Nadu, India. 2Department of Bharath University, Chennai, Tamil Nadu, India. Email: [email protected] Received: 05 January 2019, Revised and Accepted: 30 January 2020

ABSTRACT

Objective: The aim of the present study was to determine the presence of post-glenoid foramen in human skulls.

Methods: The study was carried out in 100 adult dry human skulls with 200 temporal bones on each side (right and left) which were collected from the Department of Anatomy at RVS Dental College and Hospital, Coimbatore. The selected skulls were placed on a flat table and the considerable foramen was visually identified by two investigators. The foramen was examined by a probing method to find out its patency.

Results: Of 100 skulls (200 temporal bones), only one skull showed a unilateral post-glenoid foramen on the mandibular fossa of the left side (2% of 200).

Conclusion: The emissary are considered as an important encephalic venous drainage that connects the intracranial and extracranial venous pathway through emissary foramen. If there is little variation, and rare occurrence of the emissary foramen may cause serious pathological condition. Thereby, the present study highlights one of the rare emissary foramen, the post-glenoid foramen. This anatomical study of post-glenoid foramen may help the surgeons while operating temporomandibular joint and inner ear malformation to avoid the risk of accidental bleeding during surgery.

Keywords: Post-glenoid foramen, Petrosquamous sinus, Temporal bone, Glenoid fossa. © 2020 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2020.v13i4.36782

INTRODUCTION of Anatomy at RVS Dental College and Hospital, Coimbatore. The skulls were randomly selected of unknown age and sex. The broken The post-glenoid foramen is an emissary foramen which is rarely found in or partly damaged skulls were excluded from the study, only clearly humans. It lies anterior to the external acoustic meatus in the line of fusion demarcated temporal bones of the skull were included in the study. The of the squamous and tympanic parts of the temporal bone [1]. It is also selected skulls were placed on a flat table in the dissection hall and the called as foramen jugulare spurium or foramen retroarticulare. If present, considerable foramen was visually identified by two investigators. The it transmits the petrosquamous sinus. The petrosquamous sinus is an foramen was examined by inserting a probe. The probe is a steel wire emissary connecting the intra and extracranial venous networks. It measuring about 0.5 mm in diameter and is inserted into the foramen arises from the dorsolateral portion of the transverse sinus, before the to find out the patency of the foramen. The wire is passed on to the confluence of the transverse sinus with the . Then, foramen from exterior of the skull and removed it through the interior courses over the superolateral surface of the petrous bone, either within of the skull cavity to examine the communication between the foramen an osseous groove or a complete canal called a temporal canal of Vergi [2]. and the cranial cavity. It has two drainage pathways: One anteroinferiorly into the RESULTS through the foramen retroarticulare and another one anteromedially into the pterygoid venous plexus through Of 100 skulls (200 temporal bones), only one skull showed a unilateral the foramen ovale. The petrosquamous sinus collects the middle and post-glenoid foramen on the mandibular fossa of the left side temporal superficial temporal veins, the masseterine veins, and the internal bone (2% of 200). The foramen was found backwards from the glenoid and drains into the external . It usually fossa of the temporal bone (Fig. 1). It lies anterior to the external disappears during the development of adult venous patterns in the past acoustic meatus in the line of fusion of the squamous and tympanic 3 months of prenatal life in humans [3]. part of the temporal bone. A needle was inserted to see the patency of the foramen. It was a patent opening. Since it was found in dry human Although this drainage pathway is prominent in most mammals where skull, the structure passes through it was deemed to be persistent it constitutes the major route of cerebral venous drainage, it is rarely petrosquamous sinus. of functional significance in humans, in which the and vertebral venous system represent the major outflow pathways. DISCUSSION With the evolution of primates, the foramen retroarticulare regressed The petrosquamous sinus was first described by Knott in 1881 and was as the increased its functional value [4]. In humans, named a Knott sinus. It was found in fetal life and developed from a the petrosquamous sinus, found during embryonic development, pro-otic group of veins, connecting deep temporal vein to transverse usually has disappeared by the time of birth. If this sinus persists, it sinus. This sinus runs in the angle between petrous and squamous part passes through post-glenoid foramen. In the present study, a skull with of temporal bone and emerges out through post-glenoid foramen [5]. post-glenoid foramen was found and discussed. The post-glenoid foramen is an emissary foramen which involves in extracranial venous drainage of the dural venous sinus. METHODS A total of 100 human adult dried skulls with 200 temporal bones on The course of the petrosquamous sinus is that it arises from the each side (right and left) which were collected from the Department dorsolateral portion of the transverse sinus, before the confluence Priya and Yasodai Asian J Pharm Clin Res, Vol 13, Issue 4, 2020, 42-43

Giesemann et al. reported post-glenoid foramen measuring more than 5 mm in two cases [10]. Ruiz et al. demonstrated a CT angiogram with a post-glenoid foramen in a 7-year-old patient with severe headaches but no inner ear malformation [11]. These studies correlate with the present study that of 100 skulls (200 temporal bones), only one skull showed a unilateral post-glenoid foramen on the mandibular fossa of the left side temporal bone (2% of 200) which may transmit petrosquamous sinus.

CONCLUSION Post-glenoid foramen is relatively a rare anatomical variation in human skulls. Knowledge of such variation will be useful for the surgeons while operating middle ear anomalies and while operating posterior cranial fossa.

AUTHORS’ CONTRIBUTIONS Dr. G. Priya conceptualized, designed, and drafted the manuscript. Mrs. R. Yesodai gathered the data with relevant photographs. Fig. 1: Temporal bone shows post-glenoid foramen CONFLICTS OF INTEREST of the transverse sinus with the superior petrosal sinus. It runs over The authors declare that they have no conflicts of interest. the lateral superior surface of the petrous bone. It drains either anteroinferiorly into the retromandibular vein through the foramen AUTHORS’ FUNDING retroarticulare or anteromedially into the pterygoid venous plexus No funding. through the foramen ovale. Until now, its pathway has been described in animals, predominantly in quadrupedal gait. It was rare in humans REFERENCES and is reported only by anthropologists and anatomists. In the present study, a unilateral post-glenoid foramen was observed. Since it was 1. Standring S. Grays Anatomy. The Anatomical Basis of Clinical Practice. found in adult dry human skull, the structure passes through it may be 39th ed. London: Elsevier, Churchill Livingstone; 2006. p. 486-7. persistent of petrosquamous sinus. 2. Braga J. Emissary canals in the hominoidea and their phylogenetic significance. Folia Primatol (Basel) 1995;65:144-53. th Conroy observed post-glenoid foramen in about 10% of human 3. Williams PC, Warwick R, Dyson M, Banister IH. Gray’s Anatomy. 37 ed. Edinburgh: Churchill Livingstone; 1989. p. 225-6. cadaver dissections, most often unilaterally. Through this foramen, the 4. Reymond J, Charuta A, Wysocki J. The morphology and morphometry petrosquamous sinus is directed into the retromandibular vein and of the foramina of the greater wing of the human sphenoid bone. Folia then into the [6]. Boyd observed a post-glenoid Morphol (Warsz) 2005;64:188-93. foramen in 0.6% of 1400 human skulls examined most of them <1 mm 5. Alsherhri H, Alqahtani B, Alqahtani M. Dilated petrosquamosal in size, with only one measuring 1.5 mm [7]. Wysocki detected this sinus, mastoid emissary vein and external jugular vein: A rare cause structure in 3.5% of the human skull with 0.97 mm2 as mean area [8]. of pulsatile tinnitus, vertigo and sensorineural hearing- Case report. These findings corroborate with the findings of the present study. Indian J Otol 2011;17:123-6. 6. Conroy G. The emissary foramina: Their value in platyrrhine systematic. Am J Phys Anthropol 1982;57:7-12. Marsot-Dupuch et al. reported a radiological description of 7. Boyd GI. The emissary foramina of the cranium in man and the the petrosquamous sinus associated with a post-glenoid anthropoids. J Anat 1930;65:108-21 . foramen in four cases, using high-resolution computed 8. Wysocki J. Morphology of the temporal canal and postglenoid foramen tomography (CT), complemented by magnetic resonance with reference to the size of the jugular foramen in man and selected (MR) venography. These authors suggested that a species of animals. Folia Morphol (Warsz) 2002;61:199-208 petrosquamous sinus was most frequently found in patients with 9. Marsot-Dupuch K, Gayet-Delacroix M, Elmaleh-Berges M, Bonneville F, congenital malformation of the skull base associated with Lasjaunias P. The petrosquamous sinus: CT and MR findings of a rare venous and middle ear anomalies. The surgical procedures emissary vein. AJNR Am J Neuroradiol 2001;22:1186-93. 10. Giesemann AM, Goetz GF, Neuburger J, lenarz T, Lanfermann H. in the middle ear cavity or translabyrinthine routes to the Persistent petrosquamosal sinus: High incidence in cases of complete posterior fossa may injure the petrosquamous sinus will cause aplasia of the semicircular canals. Radiology 2011;259:825-53. uncontrollable surgical bleeding or post-operative thrombosis of the 11. San Millán Ruíz D, Gailloud P, Yilmaz H, Perren F, Rathgeb JP, . The surgeons should, therefore, be aware of this venous Rüfenacht DA, et al. The petrosquamosal sinus in humans. J Anat variant and advise the patient to undergo venous CT angiography or 2006;209:711-20. MR angiography in certain cases [9].

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